A government office that’s supposed to protect consumers issued a credit wake-up call last week.

About a quarter of Americans had mistakes on their credit reports that could leave them paying more money for purchases.

The message that sends, says the Federal Trade Commission, is that everyone should check the all-important credit report.

Car, phone, home all involved

If you didn’t already know about your credit report’s capacity for affecting your life, merchants would be around to remind you.

“No good credit needed,” promises a highway billboard.

“Bad credit OK,” promises the painted window of a car dealership.

“Establish your credit here,” prompts another.

Credit comes into play not just when you buy a house or a car, but when you sign up for a cell phone or Internet plan, when you apply for a growing number of jobs, when you rent an apartment or shop for car insurance.

How to get your report

The FTC and other consumer groups won’t go so far as to say the TV and radio commercials with their snappy jingles are rip-offs. But most of those aren’t free, regardless of the company name. How would they pay for all that advertising if they gave away the product?

The best way to get that free report once a year — and you get it from all three reporting agencies — is to go online. One site, AnnualCreditReport.com, gives you instant access.

No Internet? You’ll have to wait a little longer but here’s the phone number to call so you can have the report mailed to you: 1-877-322-8228.

You can request all the reports at the same time or you can space out requests to monitor credit throughout the year.

And you can get two of the same reports free within a year’s time if that history is haunting you. Any time your credit report causes you to pay extra — say you get turned down for a loan, you’re offered higher interest rates or you have to pay a higher-than-normal deposit — the reporting agencies have to pony up an additional credit report.

How to get your score

This is the thing you normally have to pay for. But there are some ways to get the actual score without shelling out the cash.

It’s the same way you get multiple credit scores from the same agency. If a lender looks at your credit score and decides you’re not getting a loan, you can request the lender to show you the score.

That also goes for the lending officers at car dealerships or the utility company that boosts your deposit because you’re considered a risk.

Often, consumers have to ask for the score.

But some people who work with lenders hand it over without a special request.

That’s the case at Fred Caldwell Chevrolet, says General Manager Martin McKinley. For every car with financing that goes through the dealership, the buyer gets a piece of paper stating the score and explaining how that score compares with the best and the worst.

McKinley thinks most buyers have a pretty good idea how they’re going to rank.

“It’s a very educated consumer out there today,” he said. “It makes for very few surprises and we like that.”

Credit primer

When you’re talking about the interest rates you can get on loans or the deposit you might have to pay for services such as mobile phone plans, two things come into play.

1. The credit report

This is basically a breakdown of money you’ve borrowed and how good — or how poor — your track record has been for paying it back. The report is the part of your credit profile you can get for free once a year from each the major reporting agencies.

Those are Equifax, Experian and TransUnion.

2. The credit score

This is the thing you usually have to pay for, although seeing the actual number is less important than the report used by agencies to come up with the number.

Called FICO scores, the numbers range from 300 to 850. The higher the score, the better your credit. The things it measures:

- How long you’ve been obtaining credit

- What kind of credit lines you’ve received

- Payment history

- Amounts owed

- How many new credit lines you’ve received and in what period of time (numerous new cards or applications in six to 12 months and you’re likely lowering the score)

Source: Better Business Bureau

And the survey says …

- One in four consumers identified errors on their credit reports that might affect their credit scores

- One in five consumers had an error, which was corrected by a credit reporting agency after it was disputed, on at least one of their three credit reports

- Four out of five consumers who filed disputes experienced some modification to their credit report

- Slightly more than one in 10 consumers saw a change in their credit score after the credit reporting agency modified errors on their credit report

- Approximately one in 20 consumers had a maximum score change of more than 25 points and only one in 250 consumers had a maximum score change of more than 100 points.

You’ll want to contact the company that keeps track (remember, it’s either Equifax, Experian and TransUnion) AND the company that has you listed as owing what you don’t believe you owe.

In dispute letters, make sure to include account numbers related to your challenge and clearly explain mistakes, along with a request the mistake be removed or corrected. Include copies (not originals) of any documents that support your position.